Nested case-control study investigating the diagnostic role of tissue eosinophilia in adverse cutaneous drug reactions.

BACKGROUND: Although tissue-eosinophilia has traditionally been considered diagnostically supportive of adverse cutaneous drug reactions (ACDRs), studies have suggested it is neither a sensitive nor a specific finding in drug eruptions (DEs).

OBJECTIVES: Determining whether skin-tissue eosinophilia is a reliable indicator of ACDR.

METHODS: A nested case-control retrospective study conducted in a cohort of 170 patients at a single institution. Tissue eosinophilia (number of eosinophils per High Power Field (HPF)) was investigated in skin biopsies obtained from the following groups of patients who demonstrated: a)in vitro assay and telephone interview-validated cutaneous drug reactions (True DE); b)initial clinical diagnosis of ACDR but drug etiology was excluded by in vitro assay and telephone interview (False DE); c)non drug-associated cutaneous eruptions, skin tumors and nevi, randomly selected for evaluation (control).

RESULTS: Significantly higher number of eosinophils per HPF was observed in the False DE compared to the True DE group (p=0.02). The False DE group demonstrated a higher number of eosinophils (p<0.001) while the True DE group eosinophils' number was not significantly higher as compared to control (p=0.2032).

CONCLUSIONS: Tissue eosinophilia is not a reliable indicator of ACDRs. This article is protected by copyright. All rights reserved.